Anion exchange resins (bead form) including those suitable as materials for AEMs are known in the art. Generally, such resins are cross-linked and comprise functional groups with basic properties, such as amino groups, covalently linked to the base resin. Typically, anion exchange resins (bead form) and AEMs have been prepared by copolymerizing a divinyl monomer such as divinylbenzene or ethylene glycol dimethacrylate with a monomer already containing ion exchange groups, e.g, 2-sulfoethyl methacrylate, or with a monomer which after polymerization can be converted to contain ion exchange groups, such as styrene and methylstyrene (which can be converted to aminomethyl-substituted styrene) or dimethylaminopropylmethacrylamide (DMAPMA) (which can be converted to a quaternary ammonium halide after treatment with methyl chloride).
It is known also that styrene block copolymers (SBCs) can be functionalized in order to further modify their characteristics. An example of this is the addition of sulfonic acid or sulfonate ester functional groups to the polymer backbone (U.S. Pat. No. 3,577,357, U.S. Pat. No. 5,468,574, U.S. Pat. No. 7,737,224). Additionally, co-pending application Ser. No. 13/181,306 to Willis et al. (filed Jul. 12, 2011) describes modified sulfonated SBCs suitable as materials for AEMs in which the sulfonic acid or sulfonate ester functional groups are converted to sulfonamide functional groups. The sulfonamide functionalized SBCs of Willis et al. are proposed as membrane materials for electrically driven water separation processes in which they are paired with cation exchange membranes such as, e.g., disclosed in U.S. Pat. No. 7,737,224 to Willis et al.
However, there continues to be a need for AEMs which selectively transport ions and which, at the same time, exhibit mechanical integrity and dimensional stability.